Method of forging blanks, notably crankshafts

ABSTRACT

According to this method, a predetermined angular relationship is maintained between the axis of the piece of metal to be forged and the direction of the effort applied thereto, by exerting against one end of the billet maintained in a movable die a force which is neither parallel nor perpendicular to its axis, said end being guided for translation or rotation or according to any other desired path while the other end is held in a fixed die, whereby two movements, namely an axial movement and a traverse movement, are obtained concurrently for producing the desired plastic deformation.

United States Patent [72] Inventor Gabriel Ruget St. Etienne, France [21] Appl. No. 738,177

[22] Filed [45] Patented [73] Assignee [54] METHOD OF FORGING BLANKS, NOTABLY CRANKSHAFTS 3 Claims, 13 Drawing Figs.

[52] U.S. Cl 72/322, 72/386, 72/418, 72/352, 29/6 [51] Int. Cl 821d 11/04 [50] Field of Search 29/6;

[5 6] I References Cited Primary Examine rCharles W. Lanham Assistant Examiner-Michael .1, Keenan Attorney-Wenderoth, Lind & Ponack ABSTRACT: According to this method, a predetermined an gular relationship is maintained betwcenthe axis of the piece of metal to be forged and the direction of the effort applied thereto, by exerting against one end of the billet maintained in a movable die a force which is neither parallel nor perpendicular to its axis, said end being guided for translation or rotation or according to any other desired path while the other end is held in a fixed die, whereby two movements, namely an axial movement and a traverse movement, are obtained concurrently for producing the desired plastic deformation.

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lltll II III II lllll ILL I III by. MM-W 1 llllllllllllll Ill- III III III ll IIIIIII METHOD OF FORGING BLANKS, NOTABLY CRANKSHAFTS The present invention relates to a method of forging blanks consisting of a plurality of noncoaxial volumes, such as crankshafts, and of imparting thereto a continuous grained texture by means of a device having only one degree of freedom.

Many machine elements are machined from blanks consisting of several noncoaxial volumes. When such parts are to be mass-produced and have relatively reduced overall dimensions, they are manufactured by drop forging, even if their shape is complicated. On the other hand, when these blanks are bulky and have to be produced in small quantities, pressforging remains the only convenient method, since the hotworking of the metal is required for obtaining the desired mechanical properties; however, this method is time robbing and attended by various inconveniences as will appear from the following example.

The production if a single-throw crankshaft blank comprising two trunnions assembled by a disc comprises three steps:

1. Firstly a generally cylindrical bar is forged, the cross section of this bar corresponding substantially to the plate surface;

2. Then a first rough forging of the trunnions is performed by resorting to either of the following two methods:

a. cutting said trunnions from the mass of metal by oxygencutting, as illustrated in FIG. 1 of the attached drawing;

b. partially cutting the bar by using suitable angle-cutting tools, as illustrated by the superposed contours of FIG. 2;

3. The trunnion blanks are completed by a second forging step.

Obviously, this method is inadequate for obtaining relatively accurate dimensions and/or complicated shapes, so that considerable machining is required for removing the thick layer of extra metal left on the blank surface. To sum up, this conventional manufacturing method requires initially at least twice the weight of metal of the finished workpiece, and also several heat treatments and several reheating of the blank between the successive forging steps. Moreover, the cutting operations bring the central portions of the billet with a wrong orientation to the surface of the piece where the metal has the highest percentage of inclusions, thus impairing the'mechanical properties of the final workpieces, notably in connection with their stress-strain diagram.

It is the object of the present invention to provide a method of and means for forging blanks of the type set forth which are free of the inconveniences characterizing the known methods briefly mentioned hereinabove.

The forging method of this invention for making blanks of workpieces consisting of a plurality of noncoaxial volumes while imparting to these blanks a continuous grain structure is characterized in that a predetermined angular relationship is maintained between the axis of the piece of metal to be forged and the direction of the effort applied thereto by exerting against one end of the billet maintained in a movable die a force which is neither parallel nor perpendicular to its axis, said end being guided for translation or rotation or according to any other desired path while the other end is held in a fixed die, whereby two movements, namely an axial movement and a transverse movement, are obtained concurrently for producing the desired plastic deformation.

For producing a blank having the desired shape according to the method of this invention, the angular relationship between the applied force and the axis of the initial billet or blank is altered along the free length of the blank to which a plastic deformation is applied, and on the diameter of said blank. With these parameters it is possible to adjust the throw of the volumes involved (i.e. the crank medius in the case of a single-throw crankshaft) and the dimensional magnitude of the intermediate disc or plate.

According to this invention and to the available and necessary power outputs, the metal may either undergo a free plastic deformation during the forging operation (free forging) or be forcibly causedto assume a shape very close to that of the machined plate in order to minimize the machining operation to be subsequently carried out thereon (limited forging or grain-stamping), this features, according to a specific form of embodiment of this invention, being obtained by causing the two die block gripping the blank to cooperate in such a manner that upon completion of their relative movement they form a closed-die unit filled by the blank metal. By applying this particular technique the angle formed between the trunnions and the disc or plate of the single-throw crankshaft may be given a predetermined value other that and, according to the upsetting movement and the means provided for holding the movable trunnion against motion, the axes of the two trunnions may be not parallel upon completion of the forging operation, whereby extremely diversified geometrical shapes can be obtained by forging. As will be readily understoodby those skilled in the art, the method of this invention permits of obtaining with a relatively high degree of precision, that is, with the minimum excess thickness and without difficulty, a great variety of blanks consisting for example of three noncoaxial volumes such as singlethrow crankshafts. This method permits notably of working the fiberlike flow lines of the grain structure parallel to the external surface of the workpieces the axial zone of the billet or initial blank merging in their neutral fiber, the peripheral or outer zone remaining in the vicinity of their surface, thus improving considerably the stress-strain diagram of the finished product. v

This invention is also concerned with devices for carrying out the method disclosed hereinabove.

A device according to the present invention comprises essentially a movable die block carried by a slide responsive to the piston of a fluid-actuated cylinder and piston unit or like fluid-operated actuator, one end of the initial billet or blank being firmly held against motion in said die block; a fixed erossmember carrying another die block in which the other end of the initial billet is held initially, i.e. when the aforesaid actuator imparts for example a movement of translation to the billet, the position of said fixed erossmember permitting the adjustment of the above-defined parameters, and a double set of columns, tie rods or beams supporting said movable die block and said fixed erossmember in order to absorb the forging reactions directed parallel and perpendicularly to the movement of said movable die block.

The thickness of said columns, tie rods or beams by which the forging reactions are to be absorbed may be reduced by causing the planes containing their axes to intersect each other along a straight line passing substantially through the center of maximum thrust which is coincident with the center of gravity of the plate of the forged piece in the position thereof obtaining at the end of the forging operation.

According to another feature characterizing this invention the billet or initial blank may be held against movement either after the upsetting, if the two fixed and movable die blocks have only one aperture, or before the upsetting, if these die block consist each of two parts responsive to clamping members designed for assembling and disassembling them. Moreover, if desired, the slide carrying the movable die may be actuated by the movable member of a conventional press.

This invention also contemplates the provision of a device for forging crankshafts of relatively great dimensions. To this end, this device comprises a fixed erossmember adapted to carry a die block holding one end of the bar or billet to be forged and rigid with a slideway; the resulting rigid assembly is concurrently submitted to the transverse forging efforts and to the reactions resulting therefrom; a movable slide supporting the other die block holding the opposite end of the bar or billet and to which a fluid-actuated unit or the like is adapted to impart a movement, for example of translation, during which it is guided by columns and also by said slide, both die blocks having through apertures and consisting each of two parts assembled preferably along the plant containing the axis of the initial bar or billet to be forged and extending in the direction of the movement imparted thereto; moreover, the supports holding these die blocks have formed therein along the same axis a cavity in which the bar or billet can be introduced without difficulty and thus be held against motion at any desired axial point subsequent to the clamping of the two halfdies.

To obtain a complete throw by forming each cheek flange thereof separately it is possible, according to this invention, subsequent to the forging of a first plate, to combine a movement of translation intended for longitudinally positioning the second or next plate with a 180 rotation about the billet axis, in order to impart to the two cheeks or flanges the same degree of offset in relation to a reference mark linked to the billet, the die blocks being advantageously provided with means for locking the first plate or flange upset during the forging of the second plate, in order to ensure their strict parallel relationship.

In order to impart the same degree of offset to both flanges in relation to a reference mark linked to the billet, it is also possible, subsequent to theforging of the first plate, to rotate the blank twice by 180, one rotation being performed about the billet axis and the other about an axis perpendicular thereto; alternately, the set of dies may be changed for the same purpose. In all the above-described devices auxiliary retractable heating means may be provided, such as electrical induction heating elements, rows of gas burners, or other means capable of heating the blank to the desired temperature.

Other features and advantages of the invention will appear as the following description proceeds with reference to the attached drawing illustrating diagrammatically by way of example various forms of embodiment of the invention. In the drawing;

FIG. 1 shows schematically cutting the trunnions from a mass of metal by oxygencutting;

FIG. 2 illustrates schematically partially cutting a bar with angle-cutting tools;

FIG. 3 is a section taken along a plane containing the axis of the piece to be forged and the direction of the movement, to illustrate the method of this invention;

FIG. 4 illustrates diagrammatically the plastic deformation obtained by carrying out the method of this invention;

FIG. 5 illustrates a typical form of embodiment of the inven tion in the case of a limited forging operation;

FIG. 6 shows in elevational view the contour of a singlethrow crankshaft obtained by carrying out the method ,of this invention in a manner similar to that shown in FIG. 5;

FIG. 7 illustrates diagrammatically another typical form of embodiment of the invention in the case of the forging of a single-throw crankshaft of complex configuration;

FIG. 8 is a section showing a forging device according to this invention, the section being taken along the median plane of the device which contains the axis of the billet to be forged and the direction of the movement of translation imparted thereto;

FIG. 9 is a half-sectional, halfelevational view, the section being taken in a plane at right angles to the plane of the section of FIG. 8 which contains the axes of the vertical columns, the elevational view being taken at right angles to this plane;

FIG. 10 illustrates in section taken along a plane containing the axis of the die impressions and the direction of movement, a typical device designed for forging crankshafts;

FIG. 11 shown in fragmentary elevational view the initial blank for forging a multithrow crankshaft, and

FIGS. I2 and I3 illustrate diagrammatically the combined rotational movements necessary for the completeforging of a crank.

In all the figures of the drawing similar elements are designated by the same reference numerals. I

As already explained hereinabove, the method ofthis invention consists essentially in maintaining a predetermined angular relationship between the axis of the blank or billet to be forged and the direction of the force applied thereto or of the movement thus produced. The forging of a single-throw crankshaft taken by way of example herein illustrates clearly how this method simplified the forging operations and ,improves the mechanical properties of the end product.

As illustrated in FIG. 3, the initial blank is a cylindrical billet I having a diameter only slightly greater than that of the trunnions of the workpiece to be obtained; this billet has one end held in an impression or die 4 rigid with a die block 2 and its opposite end fitted in the die block 5 capped by the upper movable crossmember 3. The billet is introduced into this device either at the forging temperature or at room temperature; in this last case auxiliary retractable means such as electrical induction heating elements or rows of gas burners, or any other suitable heating means, are provided for subsequently heating the billet to the desired temperature. The movable assembly comprising the crossmember 3 and die member 5 is then lowered with a movement of translation in the direction of the arrow F, until it abuts against the piece 6 of which the thickness controls the final relative distance between the positioning tool members.

This single movement is attended by a plastic deformation with the twofold consequence illustrated in FIG. 4; in fact, this figure illustrates diagrammatically the same elements as in FIG. 3. Onthe one hand, the metal lying between the two members 4 and 5 is upset and assumes the shape of a disc or plate P of which the flat section through a plane at right angles to the initial axis of the billet is an oval, substantially an ellipse of very moderate eccentricity. On the other hand, the movable trunnion T is offset in relation to the fixed trunnion T, by a distance R corresponding to the crank throw, in a direction at right angles to the upsetting direction, The reference letter d denotes the acute angle formed by the axis of the billet with respect to the direction of the movement of translation, I being the free length of metal submitted to the plastic deformation, and e the plate thickness.

These values are linked by the following relationship:

This proves that the geometrical dimensions of the forged product are adjusted by controlling three factors. For a given plate thickness e, the radius of the throw increases with the angle d and length 1, whereby the trunnions can be offset by a desired quantity and the desired volume can be given to the disc or plate. This volume can also by obtained by altering the diameter D of the billet portion extending between the two impressions 4 and 5. In fact, it is however preferable to select for this diameter D a value differing slightly from that of said trunnions, and since the volume of the single-throw crank to be forged depends on the length of the initial billet according to the formula V=(1rD /4)l, this length is then determined by this relationship. For a given plate thickness, the first equation R=(I-e)zg d determines, from the previously determined length l the value to be given to the acute angle d. Therefore, the method of this invention, by bringing into play two independent factors, affords a high degree of flexibility in its actual use and is particularly adapted for the manufacture of blanks consisting of a pluraiity of noncoaxial volumes such as plateand-trunnion crankshafts and single or multithrow crankshafts.

Moreover, the method of the present invention improves considerably the mechanical properties of the end products and provides many advantageous features.

In fact, the forged blanks are characterized by a continuous grain structure because the cutting operation, which could not be avoided in conventional forging methods, is now eliminated and the metal fiber oriented in a direction parallel to the outer surface of the piece. The outer peripheral zone where the metal has its highest properties constantly lies in the vicinity of the surface, thus reducing considerably surface defects and flaws, and the axial zone of the blank merges in the neutral axis of the finished crankshaft and is not subjected to sudden changes of direction at points where a detrimental weakening of the metal might take place. With this specific grain structure the stress is always exerted in the longitudinal direction of the metal fiber and the mechanical strength of the end products is increased to a substantial degree. Finally, with the method of this invention the weight of the metal necessary for forging a same workpiece can be reduced considerably.

According to the machine power output available and the dimensions of the desired blank, the discs or plate can be upset up to the desired thickness by allowing the metal to assume freely its contour; this is the so-called free-forging process described hereinabove and illustrated in FIG. 4.

The plate portion of the workpiece or blank may also be given a predetermined contour by causing the elements 4, 5 and 6 to cooperate in such a manner that at the end of the forging movement they constitute together a closed die assembly filled by the blank metal; in this case a limited forging process takes place as exemplified in FIG. 5. In the forging of a plate having a well-defined shape, the upsetting force increases as the desired contour departs from the free contour which would be obtained under the same conditions, but each time the sufficient power output is available this improvement minimizes the necessary metal weight and the subsequent machining operation. Moreover, by resorting to a limited forging or fiberdie forging, it is possible to give the desired inclination to the plate in relation to the trunnions by simply modifying the angle formed between the billet axis and the joint planes of the die 6 on impressions 4 and 5. The shape of the resulting single-throw crankshaft is then similar to the one illustrated in longitudinal section in FIG. 6.

For obtaining these different blank shapes the bearing faces of impressions 4 and 5 on die 6 are kept parallel to each other throughout the plastic deformation; they form a right angle with the billet axis in the case of FIG. 5 and an acute angle in the case of FIG. 6. These bearing faces may also be nonparallel before the deformation, and become parallel during this deformation, by allowing one of the impressions 4 or 5 to pivot about an axis perpendicular to the plane formed by the billet axis and the direction of movement, as shown in FIG. 7. With this alternate form of embodiment extremely complicated crankshaft configurations can be obtained, in which the trunnions are not parallel.

It is therefore the essential feature of the method of this invention to upset the metal and, concurrently, to offset in relation to each other certain elements of the initial billet in a direction at right angles to the upsetting direction; it makes it possible to obtain multiple geometrical shapes by utilizing a movement having only one degree of freedom. Although in the foregoing the description of the properties of the end products and of the advantageous features resulting from the method of the present invention is based on a simple movement of translation, it would not constitute a departure from the spirit and scope of the invention to produce any other movement for the same purpose.

Two specific devices designed for carrying out the method of this invention will now be described by way of example. The first device is designed for forging a single-throw crankshaft and the second device is designed for forging a multithrow crankshaft.

l. Forging press for single-throw crankshafts.

During the forging operation the plastic deformation of the metal is attended by a reaction exerted in a direction forming a certain angle with respect to the direction of translation of the movable die, and the device designed for carrying out this forging method must therefore be capable of absorbing the two components of this reaction, i.e. .the one parallel and the other perpendicular to the movement. This holds true irrespective of the movement of the two die blocks towards each other; therefore, in the device according to the present invention which is illustrated by way of example in FIGS. 8 and 9, a double set of columns is provided for absorbing this compound reaction. In this example, the die block 2 consists of a slide controlled by the piston rod 8 of a fluid-operated cylinder and piston unit or like actuator (not shown), said slide bearing initially on the baseplate 7. A bracket 11 secured The billet I to be forged is introduced into the cavitie dies 4 and 6, for example by using as gripping means member such as 5, the assembly being subsequently submitted] by the actuator 8 to an upward movement of translation in the axial direction of piston rod 8. The metal-upsetting operation proper begins when the cap 5 is stopped in its recess 13 formed in the fixed crossmember 3. The forces required for this upsetting operation increase as the end position of the forging process approaches due to the increment in the crosssectional dimension of the metal to which a plastic deforma tion is applied. The center of maximum reaction is therefore the center of gravity of the plate portion of the workpiece in its final position. Therefore, in the device illustrated, the planes of the axes of columns 9 and I0 intersect each other along a straight line passing through said point; the efforts act axially on the tie rods which cannot be elongated. Moreover the bracket 11 receives concurrently the transverse upsetting force transmitted through said tie rods I0, as well as the reaction of the metal which results from the fact that the slide 2 bears against the slideway 12. Thus, with this arrangement, the forging operation cannot cause a distortion of the assembly and thus alter the shape of the forged blanks.

This device lends itself to a great number of modifications. Thus, the billet 1 may be introduced into its cavity with a certain play subsequently eliminated by the forging operation, or conversely the trunnion portions of the piece to be forged may be gripped by means of devices incorportated to this end in the crossmember 3 and dieholder 2, said last-named devices producing preponderantly an upsetting action. The assembly is operated by means of an actuator having its cylinder rigid with the bearing or baseplate 7, but it would not constitute a departure from the spirit and scope of the invention to replace this actuator by the movable or ram section of a conventional forging press for constituting a movable assembly capable of forging blanks of the single-throw crankshaft type with all the advantageous features set forth hereinabove. The reactions produced by the metal on the die elements are not necessarily transmitted through columns and tie rods, and for this purpose a frame structure may be used which is capable of withstanding both axial stress and transverse stress by resorting to any known and suitable constructional contrivances.

2. Multithrow crankshaft forging.

The above-described device may be modified and improved with a view to use the method of this invention for forging not only a pair of eccentric trunnions assembled by an intermediate plate from a relatively short billet, by imparting a continuous grain structure to the forged volume, but also complete, large size multithrow crankshafts such as crankshafts of multicylindered engines. The simplest twobearing crankshaft comprises a shaft consisting of two journals of trunnions and a crankpin disposed therebetween in an cecentric position corresponding to the crank throw radius or half-stroke, the function of this crankpin being to guide one end of a connecting rod of which the opposite end is reciprocated along a rectilinear path. The stress is transmitted from this crankpin to the trunnions and bearings through a pair of cheeks, armor flanges interconnecting them and constituting each a single-throw crankshaft with the corresponding journal, this assembly being usually referred to as a throw. Now the crankshaft of a multicylindered engine consists of a plurality of crank arms having a common shaft, these crank arms, when seen along this common shaft, being mutually offset by an angular value depending on the number of crank arms.

To apply the method of this invention to the forging of multithrow crankshafts the device used therefor must be capable firstly of forming a plate-and-crank assembly at any point along a relatively long bar and on the other hand of successively upsetting the two flanges constituting the same throw.

FIG. 10 illustrates in section taken along the plane containing the axis of the forging impressions and the direction of the upsetting movement, a device designed for overcoming these two difficulties.

According to this device the die blocks 14 and 15 are so designed that they comprise through-passages and in order'to enable them to grip a bar at any point, each die block consists of two sections assembled preferably along the plane of the section shown in the drawing; moreover, these die blocks are carried respectively by the slide 16 and fixed cros'smember 17 in whichrelatively wide outflared apertures, shown at 18 and 19 respectively, constitutes the coaxial extension of the cavities of die blocks 14 and 15, respectively. With the arrangement according to the present invention the bar to be forged can be introduced into the device through said aperture when the two sections of each die block are spaced apart, to hold this bar against motion at any desired and well-defined point,

' and eventually to forge the bar according to the method of this invention in order to form a throw or plate-and-crank assembly at this point. To this end, as in the preceding case, a fluid-operated actuator 20 is provided, its piston rod 21 being adapted to impress a movement of translation to the slide 16 guided by the columns, 22 and slideway 23. The transverse forging. reaction received by the slide 16 is transmitted through theslideways 23 to the crossmember 17 which also receives the transverse upsetting stress applied to the blank through die block 14. According to the die shape, the upset volume and the power output available, the metal will be allowed .to flow freely or alternately the die blocks 14 and 15 will coact so that at the end of the stroke a strictly definite shape will be given to the plate, this further reducing the final machining operation.

On the other hand, the initial bar from which a grain-structured crankshaft is forged is not a plain billet but a body comprising successive sections of alternately relatively large and relatively small diameter, as shown in FIG. 11. The smaller cylindrical sections are those subsequently to be converted into bearings, journals or crankpins; in the blank they have their final axial dimension but a larger diameter to take due account of the-extra thickness necessary for the machining operation. These cylinders are separated by larger ones of whichthe, length depends on the volume contemplated for each crank arm or flange, the shoulder ensuring a strict axial positioningof the blank during the upsetting operation. The premachining of the forged bar to obtain this particular initial shape is performed with due consideration for the relative positions of the bearings, crankpins and bosses determining beforehand the longitudinal position of each flange.

Under these conditions it is possible, by applying the method of this invention, and by using the device contemplated hereinabove for carrying out said method, to forge either a plateand-crank or throw element at any point along a bar, or a disc or flange of one of the crank arms of a crankshaft exactly at the position contemplated therefor.

It may be emphasized that the device illustrated in the drawing causes a trunnion, for instance, to be offset in a welldefined direction. To explain the manner in which the two cheeks flanges or arms of a same throw are forged, the choice of a system of reference axes is necessary. Referring to P16. 10, the intersection of the forging plane resulting from the movement of the movable die block 15 with the axis of this block is taken as the origin, this axis constituting the ox or abscissa line by directing same from the movable die block the fixed die block, the 0y or ordinate axis being carried by the intersection of the plane of the section with the preceding forgoing plane and so directed that the angle my be positive. When the metal is upset by allowing same to flow freely, the deformation takes place as if the center of the offset trunnion described a rectilinear path in the plane my, and the angle formed, between the axis of the initial blank and the forged cheek, flange or plate is then positive and equal to 90 as clearly shown in FIG. 12.

FIG. 13 shows clearly that for the two cheeks or flanges of a same throw the two angles of their offset are equal in absolute value but oppositely directed. Since the device permits of forging only positive offset angles, the first flange will be forged according to the axes x,o,y and the reference axes of the other flanges will be for example x o y From a mechanical standpoint it may therefore be said that when the first flange has been upset the fixed direction of the grain structure and the offset to be obtained must be caused to coincide with each other by rotating the blank.

In the case of free forging, it is only necessary to rotate the blank through about its longitudinal axis, but in the case of a limited forging it may be necessary to combine this movement of rotation with a rotation about a vertical axis, perpendicular to the plane of FIG. 10 (i.e. by turning tee bar end to end), and in certain cases, it may even be necessary to change the die blocks, according to the symmetrical arrangement of the crank flanges or arms.

Therefore, the complete forging of a crank comprises the following steps: forging the first flange, performing the movement of translation necessary for positioning the second flange, rotating the bar about its axis or an axis perpendicular thereto, changing the die blocks, and eventually forging the other flange. It is advantageous to incorporate in the'die blocks 14 and 15 means for locking the first flange during the" can be forged by taking advantage of the general features of the method (workpieces having an improved mechanical strength, lesser surface defects or flaws, which are obtained from a lower weight of initial metal) by using the device illustrated by way of example in FIG. 10. This device provides only one degree of freedom during the forging, thus suppressing the difficulties resulting from the proper timing of the movements, which is generally necessary in apparatus performing this work and due to the flange by flange forging process this device requires only a minimum power output and permits of rough forging crankshaft without bearing between two successive crankpins.

Of course, it will be readily understood by anybody conversant with the art that this invention should not be construed as being limited by the specific forms of embodiment described hereinabove and illustrated in the accompanying drawing, since many modifications may be brought thereto without departing from the spirit and scope of the invention as set forth in the appended claims.

1. A forging apparatus comprising a fixed crossmember, a pair of spaced-apart die parts relatively movable in a single direction towards one another and provided with means for holding axially spaced portions of a billet with the axis of the billet at a predetermined angle to said direction, power means movable in said direction arranged to urge said die parts towards one another in said direction so that a billet held thereby is forged into a blank having at least three nonaligned portions, a movable die block in which one of said die parts is mounted comprising a slide controlled by a piston rod of a fluid-operated cylinder and piston unit, a fixed die block supported by said fixed crossmember in which the other of said die parts is mounted, a double set of horizontal tie rods supporting said slide and said crossmember and vertical columns for absorbing forging reactions developing in directions parallel and perpendicular to the direction of movement of said movable die block.

2. A forging apparatus according to claim 1, in which said double set of horizontal tie rods and vertical columns is such that the planes containing their axes intersect along a straight fixed crossmember is integral with a slideway and said movable die block is guided by said columns and said slideway. 

1. A forging apparatus comprising a fixed crossmember, a pair of spaced-apart die parts relatively movable in a single direction towards one another and provided with means for holding axially spaced portions of a billet with the axis of the billet at a predetermined angle to said direction, power means movable in said direction arranged to urge said die parts towards one another in said direction so that a billet held thereby is forged into a blank having at least three nonaligned portions, a movable die block in which one of said die parts is mounted comprising a slide controlled by a piston rod of a fluid-operated cylinder and piston unit, a fixed die block supported by said fixed crossmember in which the other of said die parts is mounted, a double set of horizontal tie rods supporting said slide and said crossmember and vertical columns for absorbing forging reactions developing in directions parallel and perpendicular to the direction of movement of said movable die block.
 2. A forging apparatus according to claim 1, in which said double set of horizontal tie rods and vertical columns is such that the planes containing their axes intersect along a straight line passing substantially through the center of gravity of the central portion of the forged blank.
 3. A forging apparatus according to claim 1, in which said fixed crossmember is integral with a slideway and said movable die block is guided by said columns and said slideway. 